Constant amplitude and pulse width monostable multivibrator



Oct. 22, 1963 R. J. COLAO 3,108,196

CONSTANT AMPLITUDE AND PULSE WIDTH MONOSTABLE MULTIVIBRATOR Filed June20. 1960 [8- CLOCK INVENTOR. RALPH J. COLAO ATTORNEY.

United States Patent C) 3,108,196 CUNSTANT AMPLITUDE AND PULSE WIDTHMONTAELE MULTIVIBRATOR Ralph J. Colao, White Plains, NFL, assigucr toGeneral Precision, Inc, a corporation of Delaware Filed June 20, 1969,Ser. No. 37,293 8 Claims. (til. 307-3155) This invention relates tomultivibrators and more particularly to monostable multivibrators whichare suitable for use in digital logic and computer circuits.

In digital logic and computer applications it is very often necessary tohave a well regulated source of pulses which are an accurate analogue ofthe computer or master clock pulses. These pulses must not vary inamplitude or length and must have sharp leading and trailing edges.Furthermore, the multivibrator which generates these pulses must beisolated electrically from stray pulses Which would otherwise triggerthe multivibrator and cause a false output. Many of the aboverequirements can be met by using high quality components along withcareful construction techniques and adequate shielding. However, such asolution is impractical in view of the large number of thesemultiv-ibrators employed in a modern digital device and the increasedcosts attendant such a solution.

One object of this invention is to provide a monostable multivibratorwhich in response to trigger or clock pulses supplies a correspondinglypulsed output in which each individual pulse is uniform in magnitude andduration and has sharp leading and trailing edges.

Another object of this invention is to provide a monostablemultivibrator which is capable of providing well regulated output pulsesin response to high frequency clock or trigger pulses.

A further object of the invention is to provide a monostablemultivibrator which is reliable in operation and readily and easilyconstructed from standard compo nents.

The invention contemplates a monostable multivibrator circuit comprisinga pair of electron valves each having at least one control and oneoutput electrode and being biased so that one of the valves is normallyon or conducting while the other valve is normally off or nonconducting.A first electric storage means which receives the clock or triggerpulses is connected to the control electrode of the said one valve by afirst asymmetric conducting means to provide for extinguishing the onevalve output whenever a clock or trigger pulse is applied to the firststorage means. Means are provided for connecting the output electrode ofthe one valve to the control electrode of the said other valve whichturns on or conducts when the one valve is turned oil. or becomesnonconductive. A second electric storage means is connected to theoutput electrode of the other valve and to the control electrode of theone valve and to a constant current source which discharges the secondstorage means at a controlled rate, by another asymmetric conductor.Charging means are connected to the second storage means for chargingsaid means to a predetermined value whenever it has been discharged bythe constant current source.

The foregoing and other objects and advantages of this invention will bemore apparent from a consideration of the specification and drawingwherein one embodiment of the invention is described and shown in detailfor illustration purposes only.

The single FIGURE is a schematic circuit diagram of a monostablemultivibrator circuit constructed in accordance with the invention.

In the drawing, clock pulses from a source not shown are applied to aterminal 1 which is connected to the anode of a diode 3. The cathode ofdiode 3 is connected to one side of a capacitor 4 and the commonjunction of diode 3 and capacitor 4 is connected to a negative voltagesupply terminal 6 by a resistor 7. The other side of capacitor 4 isconnected to negative voltage supply 6 by a resistor 8.

A diode 9 has its anode connected to the common junction of resistor 8and capacitor 4 and its cathode to the base 10 of a transistor 12.Another diode 14 has its cathode connected to the common junction ofresistor 8 and capacitor 4 and its anode connected to ground by acapacitor 15. A voltage divider comprising two series connectedresistors 17 and 18 is connected between ground and another negativevoltage supply terminal 19 and the common junction of resistors 17 and18 is connected to the anode of diode 14 which places a biasingpotential on the anode of diode 9 to prevent stray positive pulses ornoise voltages from afiecting transistor 12.

The emitter 20 of transistor 12 is connected directly to ground and thecollector 21 is connected to voltage supply terminal 6 by a resistor 22.Collector 21 is also connected to the base 24 of transistor 25 by acompensating attenuator network 26 which network comprises a resistor 27and a capacitor 28 connected in parallel between the collector 21 andthe base 24. Network 26' matches the input impedance of transistor 25and the output impedance of transistor 12 to provide the fastestpossible rise time. Base 24 is also connected to a positive voltagesupply terminal 30 by resistor 31 and the emitter 32 of transistor 25 isconnected directly to ground.

The collector 33 of transistor 25 is connected to: a tenninal 34 towhich the output of the circuit may be connected. Terminal 34 isconnected to voltage source terminal 6 by a resistor 35. A seriesconnected resistor 36 and a Zener diode 37 are connected between sourceterminal 6 and ground and the common junction of the resistor and diodeis connected to terminal 34 by a diode 38 which has its anode connectedto the common junction and its cathode connected to terminal 34.

A resistor 40, a capacitor 41, a diode 42 and another resistor 43 areconnected in series between source terminal 6 and ground. The commonjunction of resistor and capacitor 41 is connected to terminal 34 by adiode 45 which has its cathode connected to the common junction and itsanode connected to terminal 34. The common junction of capacitor 41 anddiode 42 is connected to the base 10 of transistor 12 by a diode 46which has its cathode connected to base 10 and its anode connected tothe common junction of capacitor 41 and diode 42. The diode 42 isconnected so that its cathode and the anode of diode 46 are connected tothe same common point. Base Ill of transistor 12 is connected to voltagesource terminal 19 through a transistor 48 and an adjustable resistor49.

The collector 50 of transistor 48 is directly connected to the base 10and the emitter 51 is connected through variable resistor 49 to source19.

The base 52 of transistor 48 is connected to ground by a resistor 53 andto source terminal 19 by a Zener diode 54 to provide a substantiallyconstant voltage on the base 52. The collector 21 of transistor 12 isalso connected to source 19 by a diode 56 which has its cathodeconnected to collector 21 and its anode connected to the source terminal19.

In operation negative clock pulses applied to terminal 1 chargecapacitor 4 to a negative voltage which is comparable to the voltage ofthe clock pulse. When the clock pulse returns to its Zero voltage level,capacitor 4 discharges through diode 9 which causes the base 10 oftransistor 12 to become positive and, thus, prevents further conductionthrough transistor 12. The negative voltage swing of the collector 21 oftransistor 12 is applied to the base 24 of transistor 25 through thecompensating attenuating network 26. This negative voltage turnstransistor 25 on to institute the monostable multivibrator action. Whentransistor 25 is turned on, the charge on capacitor 41 is transferred tothe base 10 of transistor 12 and maintains it in the off condition.However, at the same time, capacitor 41 is discharged through theconstant current source which is comprised of transistor 43, adjustableresistor 49, resistor 53 and Zener diode 54.

The rate at which condenser 41 is discharged through the constantcurrent source will be a function of variable resistor 49 and anadjustment of this resistor will vary the length of the pulses output atterminal 34. The entire circuit will return to the original or startingstate, that is, with transistor 12 conducting and transistor 25 cut offwhen the charge on capacitor 41 diminishes to zero. When this conditionis obtained, the constant current source then supplies biasing currentto the base 19 of transistor 12. When transistor 12 conducts, capacitor41 will recharge to the negative voltage it had previously attainedthrough resistor 43, diode 42 and resistor 49.

Diode 46 prevents positive voltage from capacitor 4 from affecting thecharge on capacitor 41. Thus, the pulse length of the multivibrator isunaffected by variations in the amplitude of the clock pulse applied toterminal 1. In order that initial conditions, that is those conditionsprevailing prior to the application of a clock pulse at the terminal 1,remain constant with respect to capacitor 41, the Zener diode 37 clampsthe terminal 34 at a constant voltage level.

Another of the features of this circuit is the effect produced by diode45 which prevents cross-coupling capacitor 41 from affecting thesharpness of the trailing edge of the output wave form since itdecouples the capacitor from the collector load resistor 35 during thiscritical period.

The circuit described has been constructed so as to provide outputvoltages which switch between l volts and -O.2 volt. The followingvalues will provide this output. With reference to the variable resistor49, the values given in the table range from 3.9 to 7.5K ohms to providethe exact pulse length required.

Voltages 6 volts 28 19 do l0 3t) do +16 Clock do Resistors 17 ohms 27043 do 470 1K do 1.5K 22,35, 36 do 2.7K 27 do 3.3K

Although only one embodiment of the invention has been shown anddescribed in detail for illustration pur poses, it is to be expresslyunderstood that the invention is not to be limited thereto.

What is claimed is:

1. A monostable multivibrator circuit comprising, a pair of electronvalves each having at least one control and one output electrode, saidvalves being biased such that one valve is normally on or conducting andthe other is normally off or nonconducting, first electric storage meansfor receiving triggering pulses, first asymmetric conducting means forconnecting the first electric storage means to the control electrode ofthe said one valve to extinguish conduction when a triggering pulse isapplied to the first electric storage means, means for connecting theoutput electrode of the said one valve to the input electrode of thesaid other valve to turn the said other valve on when the said one valveis turned off, second electric storage means connected to the outputelectrode of the said other valve and by an asymmetric conductor, whichis arranged to oppose the conduction from the first electric storagemeans, to the control electrode of the said one valve and to a constantcurrent source which discharges said second storage means at acontrolled rate, and means for charging said second storage means to apredetermined value each time it is discharged by the said constantcurrent source.

2. A monostable multivibrator circuit comprising a pair of transistorseach having one control and one output electrode, said transistors beingbiased such that one is normally on or conducting and the other isnormally oil or nonconducting, first asymmetric conducting means forconnecting a first storage means to the control electrode of the saidone transistor to extinguish conduction Whenever a triggering pulse isapplied to the first electric storage means, means for connecting theoutput electrode of the said one transistor to the control electrode ofthe said other transistor to turn the said other transistor on when thesaid one transistor is turned off, second electric storage meansconnected to the output electrode of the said other transistor and by anasymmetric conductor, which is arranged to oppose the conduction fromthe first electric storage means, to the control electrode to the saidone transistor and to a constant current source which discharges thesecond storage means at a predetermined rate, and means for rechargingthe second storage means after it has been discharged by said constantcurrent source.

3. A monostable multivibrator circuit as set forth in claim 1 in whichthe transistors are connected such that the base is the controlelectrode and the collector is the output electrode.

4. A monostable multivibrator circuit as set forth in claim 1 in whichsaid first and second electric storage means are condensers and theasymmetric conducting means are diodes.

5. A monostable multivibrator circuit comprising a pair of transistorswhich are biased so that one is normally on or conducting and the otheris normally off or nonconducting, a first capacitor for receivingtriggering pulses, a diode connecting the first capacitor to the base ofthe said one transistor to extinguish conduction when the triggeringpulse is applied to the first capacitor, means for connecting thecollector of the said one transistor to the base of the said othertransistor to turn the said other transistor on when said one transistoris turned off, a second capacitor connected to the collector of the saidother transistor and by a diode, which is arranged to oppose theconduction from the first capacitor, to the base of the one tnansistorand to a constant current source which discharges the second capacitorat a controlled rate, and means for charging the second capacitor to apredetermined value each time it is discharged by the constant currentsource.

6. A monostable multivibrator circuit as set forth in claim 5 in whichthe means for charging the second capacitor comprises a resistivenetwork and a diode connected in series with the capacitor to a voltagesource.

7. A monostable multiviorator circuit comprising a pair of transistorswhich are biased so that one is normally on or conducting and the otheris normally off or noncondncting, a first capacitor for receivingtriggering pulses, a diode connecting the first capacitor to the base ofthe said one transistor to extinguish conduction when the triggeringpulse is applied to the first capacitor, means for connecting thecollector of the said one transistor to the base of the said othertransistor to turn the said other transistor on when said one transistoris turned off, a diode for connecting the collector of the secondtransistor to a second capacitor, another diode, which is arranged tooppose the conduction from the first capacitor, connecting said secondcapacitor to the base of the one transistor and to a constant currentsource which discharges the second capacitor at a controlled rate, andmeans for charging the second capacitor to a predetermined value eachtime it is discharged by the constant current source.

8. A monostable multivibrator circuit as set forth in claim 7 in whichthe means for charging the second capacitor comprises a resistivenetwork and a diode connected in series with the capacitor to a voltagesource.

References Cited in the file of this patent UNITED STATES PATENTS2,827,574 Schneider Mar. 18, 1958 2,90i1,6'39 Woll Aug. 25, 19592,976,428 Parkhill et a1. Mar. 21, 1961 2,976,432 Geckle Mar. 21, 19612,986,649 Wray May 30, 1961

1. A MONOSTABLE MULTIVIBRATOR CIRCUIT COMPRISING, A PAIR OF ELECTRONVALVES EACH HAVING AT LEAST ONE CONTROL AND ONE OUTPUT ELECTRODE, SAIDVALVES BEING BIASED SUCH THAT ONE VALVE IS NORMALLY ON OR CONDUITING ANDTHE OTHER IS NORMALLY OFF OR NONCONDUCTING, FIRST ELECTRIC STORAGE MEANSFOR RECEIVING TRIGGERING PULSES, FIRST ASYMMETRIC CONDUCTING MEANS FORCONNECTING THE FIRST ELECTRIC STORAGE MEANS TO THE CONTROL ELECTRODE OFTHE SAID ONE VALVE TO EXTINGUISH CONDUCTION WHEN A TRIGGERING PULSE ISAPPLIED TO THE FIRST ELECTRIC STORAGE MEANS, MEANS FOR CONNECTING THEOUTPUT ELECTRODE OF THE SAID ONE VALVE TO THE INPUT ELECTRODE OF THESAID OTHER VALVE TO TURN THE SAID OTHER VALVE ON WHEN THE SAID ONE VALVEIS TURNED OFF, SECOND ELECTRIC STORAGE MEANS CONNECTED TO THE OUTPUTELECTRODE OF THE SAID OTHER VALVE AND BY AN ASYMMETRIC CONDUCTOR, WHICHIS ARRANGED TO OPPOSE THE CONDUCTION FROM THE FIRST ELECTRIC STORAGEMEANS, TO THE CONTROL ELECTRODE OF THE SAID ONE VALVE AND TO A CONSTANTCURRENT SOURCE WHICH DISCHARGES SAID SECOND STORAGE MEANS AT ACONTROLLED RATE, AND MEANS FOR CHARGING SAID SECOND STORAGE MEANS TO APREDETERMINED VALUE EACH TIME IT IS DISCHARGED BY THE SAID CONSTANTCURRENT SOURCE.